1. Field of the Invention
The extractor device according to the invention relates to the presses used for the hot extrusion of metal tubes through a die. It more particularly relates to the extrusion of steels of all types or other metals or alloys at a temperature generally above 900.degree. C. with the use of glass as the lubricant.
2. Background of the Related Art
At the end of tube extrusion, when the thrust of the press tool is stopped, upstream of the die there is generally an untransformed metal portion. This portion can be of varying size representing several percent of the weight of the starting billet and can have variable shapes. This unextruded metal portion can e.g. be in the form of a mass remaining blocked at the end of extrusion in the front part of the container, or can be in the form of a more or less regular tube end.
It is therefore generally necessary to cut the tube off as close as possible upstream of the die in order to be able to extract it from the die from the downstream end. The tube is cut off following an adequate moving back of the container and the extrusion needle, whose downstream end is engaged in the tube downstream of the die and this moving back operation generally causes a slight moving back in the upstream direction through the die of the extruded tube. Once cutting off has taken place, the tube is extracted downstream through the die generally by forcing back the upstream end of the tube by the metal residue jammed in the container and which is again advanced.
This operation of extracting the tube from the die by forcing the upstream towards the downstream end suffers from the major disadvantage of making unusable for the preparation of the following extrusion cycle, both the container and the needle and leads to an overall and very large reduction in the extrusion rates.
Attempts have been made to obviate this operation of forcing the tube from the upstream to the downstream end by developing, according to the invention, an extractor device mounted downstream of the die and which permits, on the basis of a tube having an end blocked upstream of the die, but which is freed from the untransformed metal portion, to extract said tube through the die without causing local or general deformations or local or general defects on the hot tube, e.g. in the form of incrustations or dimensional changes as a result of the elongation resulting from the application to the tube of the tensile stresses necessary for the extraction.
The end blocked upstream of the die, but which is freed from the untransformed metal portion can be a cutoff end, as explained hereinbefore and in which the section may or may not have a rough edge, or can be a more or less regular end resulting from an almost complete extrusion, but which has remained in the die or upstream thereof, the case of almost complete extrusion being relatively rare.
Investigations have also taken place into the possibility of eliminating whenever the tube metal quantity still engaged in the die after extrusion is relatively small, the operation of cutting off the tube in the upstream area of the die. Attempts have also been made to obtain such a result without damaging the tube walls by clamping using a clamp or any other tool. The possibility of avoiding any significant extension of the operating cycle, which could be caused by carrying out a supplementary operation has also been investigated.